Infrared phonon activity in pristine graphite

TL;DR

This paper investigates the infrared phonon peak in pristine graphite, explaining its spectral features through a charged-phonon theory that considers electronic particle-hole asymmetry.

Contribution

It provides a combined experimental and theoretical analysis revealing the role of particle-hole asymmetry in phonon activity in graphite.

Findings

Large spectral weight explained by charged-phonon theory

Fano asymmetry attributed to electronic particle-hole asymmetry

Theoretical model aligns with experimental observations

Abstract

We study experimentally and theoretically the Fano-shaped phonon peak at 1590 cm$^{-1}$ (0.2 eV) in the in-plane optical conductivity of pristine graphite. We show that the anomalously large spectral weight and the Fano asymmetry of the peak can be qualitatively accounted for by a charged-phonon theory. A crucial role in this context is played by the particle-hole asymmetry of the electronic $\pi$-bands.